Process for making hydroxamic acids



absence of water.

Patented Aug. 1, 1939 UNITED STATES ATEN ornes PROCESS FOR MAKING HYDROXAMIG ACIDS Samuel B. Lippincott, Terre Haute, Ind., as-

signor to Purdue Research Foundation, La Fayette, Ind., a corporation of Indiana No Drawing. Application July 3, 1937, Serial No. 151,837

6 Claims.

por phase nitration of saturated hydrocarbons in accordance with the process of U. S. Patent No. 1,967,667 by H. B. Hass, E. B. Hodge, and B. M. Vanderbilt. The nitroparaflins produced by this process from petroleum hydrocarbons constitute an advantageously cheap source of aliphatic compounds for the production of organic chemicals. I have now found that hydroxamic acids may be produced from these nitro compounds with satisfactory yields and conversions by the reaction of the nitrohydrocarbons with strong acids under the controlled conditions as hereinafter set forth. It has been shown in my copending U. S. Serial Numbers 148,107, 148,108 and 148,109, filed June 14, 1937, that carboxylic acids may be readily prepared by the reaction of primary nitrohydrocarbons with strong acids under certain conditions. I have now discovered that under certain different well defined conditions the treatment of the same nitro compound with a strong acid will unexpectedly give rise to the production of the corresponding'hydroxamic acid as a major product. The process of my present invention may be briefly described as comprising subjecting the primary nitrohydrocarbon at a temperature substantially under C. to the action of a strong acid in the complete or almost complete The reaction which takes place may be represented as follows: 7

NOH

RCHzNOz RC The strong acid utilized as the converting agent apparently enters into the reaction in an intermediate stage, but may be recovered at the conclusion of the reaction, and from this standpoint may be considered as a catalyst.

The nitrohydrocarbons which are suitable for my process are the primary nitroparaflins, the cycloalkyl and aryl substituted primary nitroparaffins, and the like. The primary nitroparaffins are very satisfactory for my process, and among these nitroethane, l-nitropropane, l-nitrobutane and 1-nitro-2-methylpropane are particularly suitable. It is to be understood however, that my invention is not to be limited to any particular nitrohydrocarbon of this series but is generally applicable to all nitrohydrocarbons containing the group CH2NO2.

, some of these acids will be less advantageous The acids which may be used to effect the conversion of the nitrohydrocarbons to hydroxamic acids in my process may be any acids having dissociation constants in excess of 10- The term acid, in this connection, signifies any acid having a. mineral acid grouping or a carboxylic acid grouping. Among such acids may be mentioned sulfuric, phosphoric, 'dichlcracetic, oxalic,,;ben

zene sulfoniap-toluene sulfonic, and beta-naphthalene sulfonic acids. It will be evident, of 10 course, that although any acid having a diss'ociation constant in excess of the specified value will serve to effect the conversion of the nitro-:compound into the corresponding hydroxamic acid,

5 than others. The acid employed should preferably be neither strongly oxidizing nor strongly reducing, in order to minimize any tendency for decomposition of the hydroxamic acid. For this -I prefer to employ sulfuric acid. However, it is to be understood that my invention is not limited to the use of this or any of the other acids specifically mentioned.

I have found that the reaction will occur over' a wide range of ratios of acid to nitrohydrocarbon, but that preferably at least 1 mole of acid per mole of nitrohydrocarbon should be employed. 35 The optimum ratio may inany particular case be. readily determined by simple preliminary experiments. v

, The reaction temperatureis preferably kept be- I low 120 C. since at higher temperatures the hy- 40 droxamic acid tends to decompose. However, the optimum temperature may vary widely for each reaction and the various concentrations of acid used.

I have found that for satisfactory yields of hydroxamic acids only minimal concentrations of water should be present in the reaction mixture, especially when the reaction is carried out at elevated temperatures. I prefer, therefore, to employ anhydrous acids as the converting acids, although slightly less concentrated acids may be employed with resulting lower yields of hydroxamic acids. Although water should be present in only minimal concentrations during the main reaction, I have found that for optimum yields 55 Example I Fifty-eight parts by weight of 95% sulfuric acid Were dropped into 50.5 parts of cold l-nitropropane and the resulting mixture was allowed to stand at room temperature. After nine days, a 12% conversion to propionohydroxamic acid was obtained.

Example II A mixture of 101 parts by Weight of l-nitropropane and 110 parts of 100% sulfuric acid was allowed to stand at room temperature for 2'7 days. Propionohydroxamic acid was recovered from the reaction mixture corresponding to a 35% conversion to the crude product.

Example III A mixture of 101 parts by weight of l-nitropropane and 110 parts of 100% sulfuric acid was maintained at 37 C. for ten days. At the end of this time, analysis of the reaction mixture indicated 30% conversion of the nitropropane to propionohydroxamic acid.

Example IV A mixture of 101 parts by weight of l-nitropropane and 110 parts of 100% sulfuric acid was maintained at a temperature of 80 to 100 C. for 20 hours. Propionohydroxamic acid was recovered from the reaction mixture corresponding to a 44% .conversion into the crude product.

The hydroxamic acid may be isolated from the resulting solution by any suitable procedure. I have found the following to be satisfactory for the isolation of propionohydroxamic acid from a reaction mixture utilizing sulfuric acid as the converting acid. After the reaction is complete, the mixture is cooled and poured into ice water. While cold, the sulfuric acid is neutralized by adding powdered calcium carbonate, and the resulting calcium sulfate is then filtered off- The filtrate is concentrated at reduced pressure, the temperature varying from about 40 to 60 C., refiltered and concentrated to a thick syrup. This syrup will then crystallize to a crude product on seeding with a few propionohydroxamic crystals. The crude hydroxamic crystals may be readily purified by recrystallization from a suitable solvent. It is to be understood that my invention is in no way to be limited to the method for obtaining the hydroxamic acid from the reaction mixture. The foregoing method is only an example of how this may be done.

It is also to be understood, of course, that the above examples are illustrative only, and my inventtion is not to be construed as limited to the particular materials or procedures set forth. Numerous modifications of procedure will naturally occur to those skilled in the art, and my invention includes any such modifications or the useof any obvious equivalents.

My invention now having been described, what I claim is:

1. A process for the production of hydroxamic acids from primary nitrohydrocarbons which comprises subjecting the nitrohydrocarbon to the action of an acid having a dissociation constant in excess of 10* and which is not strongly oxidizing in character, the reaction being efiected in the presence of minimal concentrations of water.

2. A process for the production of hydroxamic acids from primary nitrohydrocarbons which comprises subjecting the nitrohydrocarbon to the action of an acid having a dissociation constant in excess of 10 and which is not strongly oxidizing in character, the reaction being effected in the absence of water.

3. A process for the production of hydroxamic acids from primary nitrohydrocarbons which comprises subjecting the nitrohydrocarbon to the action of an acid having a dissociation constant in excess of 10- and which is not strongly oxidizing in character, at a temperature from about room temperature to about 120 C. and in the absence of water.

4. A process for the production of hydroxamic acids from primary nitroparaffins which comprises subjecting the nitroparaflin to the action of sulfuric acid at a temperature from about room temperature to about 120 C. in the absence of water.

5. A process for the production of hydroxamic acids from primary nitroparaffins which comprises subjecting the nitroparaffin to the action of ,phosphoric'acid at a temperature from about room temperature to about 120C. in the absence of water.

6. A process for the production of hydroxamic acids from primary nitroparaffins which comprises subjecting the nitroparafiin to the action of benzene sulfonic acid at a temperature from about room temperature to about 120 C. in the absence of water.

SAMUEL B. LIPPINCOTT. 

